The present invention relates to a soft magnetic thin film and more particularly to a soft magnetic thin film having high saturation magnetic flux density and suitable for a magnetic transducer head.
In magnetic recording apparatus such as, for example, video tape recorders (VTRs), researches are being made towards increasing the recording density and the frequency of the recording signals. In keeping pace with the tendency towards high density recording, so-called metal powder tapes making use of the powders of the ferromagnetic metals, such as Fe, Co or Ni, as magnetic powders, or so-called evaporated metal tapes in which the ferromagnetic metal material is deposited on the base film, are also used as the magnetic recording medium. By reason of the high coercive force Hc of said magnetic recording medium, head materials of the magnetic head for both recording and replaying are required to have a high saturation magnetic flux density Bs and high permeability .mu.. For instance, the ferrite material used frequently is low in saturation magnetic flux density Bs, whereas permalloy presents a problem in abrasion resistance.
Fe-Al-Si alloys, so-called sendust alloys are practically used to satisfy such requirement.
In the sendust alloy, it is preferable to have magnetostriction .lambda.s and crystalline magnetic anisotropy K both about zero. The composition of the sendust alloy for use in a magnetic transducer head is determined by considering the magnetostriction and the crystalline magnetic anisotropy. Thus the saturation magnetic flux density is uniquely determined by the composition. In sendust alloy, the saturation magnetic flux density is about 10000 to 11000 gauss at most, considering the soft magnetic property for use in magnetic transducer head.
Amorphous magnetic alloys are known which have a wide permeability at high frequency band and high saturation magnetic flux density.
The amorphous magnetic alloy has the saturation magnetic flux density of 12000 gauss at most when considering the soft magnetic property. The amorphous magnetic alloy is not stable upon heat treatment, and changed into crystalline phase by heat treatment at, for example, 500.degree. C. which results in the loss of the magnetic characteristics that the amorphous phase had. In manufacturing manetic transducer heads, various heat treatments are employed, for example, melt bonding of cores by glass at an elevated temperature. However in using amorphous magnetic mateiral, there are some restrictions on temperature in the manufacturing process. Thus the prior art magnetic materials for magnetic transducer head core are still not satisfactory in saturation magnetic flux density to fully use the capability of a high coercive force magnetic recording medium for high density recording.